Pulmonary arterial hypertension (PAH) is a fatal disorder of the lung circulation in which accumulation of vascular cells progressively obliterates the pulmonary arterioles. This results in sustained elevation in pulmonary artery pressure leading eventually to right heart failure. Approximately, 70% of familial and 20% of sporadic idiopathic PAH cases are caused by mutations in the bone morphogenetic protein receptor type 2 (BMPR2). Nonsense mutations in BMPR2 are amongst the most common mutations found, where the insertion of a premature termination codon (PTC) causes mRNA degradation via activation of the nonsense-mediated decay (NMD) pathway leading to a state of haploinsufficiency. Ataluren (PTC124), a compound that permits ribosomal read-through of premature stop codons, has been previously reported to increase BMPR2 protein expression in cells derived from PAH patients harbouring nonsense mutations. In this study, we characterized the effects of PTC124 on a range of nonsense BMPR2 mutations, focusing on the R584X mutation both in vitro and in vivo. Treatment with PTC124 partially restored BMPR2 protein expression in blood outgrowth endothelial cells (BOECs) isolated from a patient harbouring the R584X mutation. Furthermore, a downstream BMP signalling targets, Id1, were rescued by PTC124 treatment. Mutant cells also exhibited increased LPS-induced permeability which was reversed by PTC124 treatment. Increased proliferation and apoptosis in R584C BOECs were also significantly reduced by PTC124. Moreover, oral PTC124 increased lung Bmpr2 protein expression in mice harbouring the R584X mutation (Bmpr2+/R584X). Our findings provide support for future experimental medicine studies of PTC124 in PAH patients with specific nonsense BMPR2 mutations.